1. Field
This invention relates to the inhibition of corrosion metals and, more particularly, to the inhibition of corrosion of ferrous metals which are exposed to acids, brines, oxygen and other corrosive materials.
Ferrous metals, particularly non-corrosion resistant steels, are very susceptible to corrosion by acids, brines, carbon dioxide, oxygen and many other substances. In spite of the fact that crude oil removed from the ground contains large amounts of these corrosive substances non-corrosion resistant steels are widely used in drilling for and the removal of oil from the ground, and for its transportation and storage after it has been pumped to the surface. The reason for this, of course, is that corrosion resistant ferrous metals, such as nickel-chromium stainless steel are too costly for general use and most non-ferrous metals, in addition to being very costly, lack the strength required in oil-producing and handling equipment.
2. Prior Art
In order to extend the useful life of ferrous metals which are exposed to highly corrosive substances the surfaces of the metals are generally treated with corrosion inhibiting chemicals. This is accomplished by direct application of the inhibitor to the metal surface where possible or, if the surface to be protected is the interior of a pipeline or vessel, by injecting the inhibitor into the fluid being carried through the pipeline or into the vessel.
U.S. Pat. No. 3,231,493, discloses the use of polyamide adducts as corrosion inhibitors. These adducts are prepared by reacting organic acids; high boiling amine residues prepared by reacting monoethanolamine, ethylenediamine or ethylene glycol with ammonia; and an alkylene oxide, alkylene carbonate or an aralkylene carbonate. U.S. Pat. No. 2,944,968 discloses the use of diamides made from polyalkyleneamines and monocarboxy naphthenic acids as ferrous metal corrosion inhibitors. The alkylene portion of the polyalkyleneamines may consist of as many as six carbon atoms. Other U.S. Pat. Nos. of interest include 2,640,029, 2,736,658, 2,901,430, 2,976,179 and 3,134,759.